Dynamic DNS - cannot switch off

Anybody else encountered this? I’m trying to switch off my dynamic DNS but the router won’t let me. I get a chrome popup window that says “Please enter the password. [OK]” Click okay and it looks like the dynamic DNS is off but if I refresh the page it is still on.

 

I figured out you can turn it off by clearing all the fields including the hostname and username fields then switch the button to OFF and Save.